This invention relates generally to optical image scanners and more specifically to an optical image scanner using lens arrays, where the distance, from the surface where an image is being scanned, to the opposite outer surface of the scanner, is relatively short.
Image scanners, also known as document scanners, convert a visible image on a document or photograph, or an image in a transparent medium, into an electronic form suitable for copying, storing or processing by a computer. An image scanner may be a separate device, or an image scanner may be a part of a copier, part of a facsimile machine, or part of a multipurpose device. Reflective image scanners typically have a controlled source of light, and light is reflected off the surface of a document, through an optics system, and onto an array of photosensitive devices. Transparency image scanners pass light through a transparent image, for example a photographic positive slide, through an optics system, and then onto an array of photosensitive devices. The optics system focuses at least one line, called a scanline, on the image being scanned, onto the array of photosensitive devices. The photosensitive devices convert received light intensity into an electronic signal. An analog-to-digital converter converts the electronic signal into computer readable binary numbers, with each binary number representing an intensity value.
There are two common types of image scanners. In a first type, the length of the photosensor array is much less than the length of the scanline. For the first type, a spherical reduction lens is commonly used to focus the scanline onto the photosensor array. In a second type, the length of the photosensor array is the same length as the scanline. For the second type, it is common to use Selfoc(copyright) lens arrays (available from Nippon Sheet Glass Co.), in which an array of rod-shaped lenses is used, typically with multiple photosensors receiving light through each individual lens. The optical path length (the distance from the image being scanned to the photosensor array) of Selfoc lens arrays is relatively short compared to the optical path length of a spherical reduction lens. For example, the typical optical path length for a reduction lens in an image scanner is hundreds of millimeters, and the typical optical path length for a Selfoc lens array is tens of millimeters. However, there is a need for even smaller scanners, for example, for use with portable digital personal appliances.
An optical image scanner uses one or more reflecting surfaces to provide a light path through a lens array, where the optical path through the lens array is non-perpendicular to the surface of the image being scanned. As a result, the distance, from the surface where an image is being scanned, to the opposite outer surface of the scanner, is relatively short compared to scanners in which lens arrays are perpendicular to the image being scanned. An illumination source may be provided as part of an assembly that includes the lens array. Alternatively, the assembly may be integrated with a video display, or placed adjacent to a video display, and the video display may be used as the illumination source. For example, a scanner may be used in conjunction with a hand-held computer, or with a digital photo frame. The assembly may optionally monitor the intensity and color of the illumination source during scanning. The assembly may also optionally image the display, enabling screen prints, or remote scanning of a computer screen for technical assistance.